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File: ftp://cherupakha.media.mit.edu/pub/projects/miniboard/docs/mbext20.txt
More info:   fredm@media.mit.edu
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ANNOUNCING THE MINI BOARD 2.0 EXTENDED

Fred Martin
fredm@media.mit.edu
Sun Mar  6 12:09:01 1994


The message is to announce the first revision of the Mini Board 2.0
design since it was released in June 1992.  The Mini Board 2.0
Extended is a small revision of the original design.  It is 0.45
inches longer than the original.  The extra length adds
following features:

  * two real mounting holes so the board can be bolted down to
    something.

  * 2.1 mm coaxial DC power jack as an alternate method to apply power
    to the board.  Either the original screw terminal block or the DC
    power jack may be used.

  * SPDT slide switch to switch power from DC jack on and off.  If
    power is applied from screw terminal block, slide switch is
    not part of the power circuit.

  * the extra .45" of length may be chopped off to save space; the
    above three features are then lost.

In addition to the above features supported on the extra board area,
the main board area has been revised to include the following:

  * TTL-level 6811 TxD and RxD pins exposed to female header jacks.
    These can be used to communicate with other TTL level async serial
    devices, or can be temporarily jumpered together and tied via 10K
    resistor to +5v to allowing booting of 512 byte of EEPROM 'A1
    versions of the 6811.

  * if IRQ button is not installed, a Dallas Semiconductor DS1233
    "econo-reset" chip may be mounted instead.  This chip assures
    correct power-on reset operation of 6811 for "mission critical"
    applications.  (Most of the time the 6811 boots properly when
    power is applied, but the DS1233 may be used to insure that it
    -always- boots properly.)


I hope that these new features will be valuable to the community of
Mini Board users.

	-Fred


Additional notes:

1.  A PostScript file of the silkscreen of the Mini Board 2.0 Extended
may be retrieved from the anonymous FTP server
cherupakha.media.mit.edu (IP address 18.85.0.47) in file
pub/projects/miniboard/docs/mbext20.PS.Z (a Unix compressed file).
The file illustrates all of the new features except the two mounting
holes, which are not marked on the silkscreen.  The mounting holes are
located in the obvious places: above the slide switch and below the DC
power jack.

2. The slide switch is part number CKN5001-ND from Digikey.  The DC
power jack is part number SC1047-ND from Digikey.  (Both of these part
numbers are present on the silkscreen.)

3.  In order to use the Dallas Semiconductor DS1233 chip, an
additional 0.1 uF capacitor is required.

----
Fred Martin | fredm@media.mit.edu | (617) 253-5108 | 20 Ames St. Rm. E15-320
Epistemology and Learning Group, MIT Media Lab     | Cambridge, MA 02139 USA